Google Maps is one of the most popular mapping tools when travelling overseas.
On average, Google Maps doesn't use much mobile data, it's approximately 5MB per 30 minutes of driving.
However, if you are looking for the most economical method for finding your way around town, Offline Mapping is the solution.
You can save an area from Google Maps to your phone or tablet and use it 'offline'. Make sure you do this while connected to WiFi.
Be aware, this will limit functions of some Google Maps features such as traffic information, alternate routes, lane guidance or walking and cycling directions.
You will still have full access to driving directions so you can get from A to B.
Other excellent offline mapping APPs are Maps.me, Sygic offline maps, OsmAnd and MapFactor.